Electromotor-driven mechanical stoker



1944- J. H. JACOBSEN 2,356,590

ELEGTROMOTOR-DRIVEN MECHANICAL STOKERS Filed July 16, 1940 2 Shets-Sheet1 Big! Screen \-\Q\Q UQLObSQQ INVENTOIQ,

Q7 WWW/x aw m Paten tecl Aug. 22, 1944 UNITED STATES PATENT OFFICE.lorgen Helge Jacobson, Hellerup, Denmark; vested in the Alien PropertyCustodian Application July 16, 1940, Serial No. 345,866 In Denmark July25, 1939 1 Claim.

This invention relates to improvements in mechanical stokers,particularly of the electric motor-driven type.

It is common practice for steam boilers and hot water boilers inapartment houses, schools, cottages and the like, and for industrialboilers to be fired by mechanical stokers, in which the fuel.

is charged into the furnace by means of a feeding device, and in whichthe combustion air is supplied under pressure from one or more fans toan air chamber located below or around, or both below and around thefurnace grate.

The consumption of heat in most heating plants is subject to manyvariations while in operation, and for this reason adjustments of thefuel feeding member of the mechanical stoker are required during the dayand/or night. For this purpose a manually operable gear operativelyconnected between the driving parts and the fuel feeding device of thestoker is generally employed. However, adjustments made by this meanscannot in practice follow accurately the relatively large and frequentvariations in the amount of heat required.

Further, in prior stoker installations, should the driving element, suchas the electric motor, fail the stoker is rendered inoperative and theproduction of heat is stopped. Heretofore the only available relief fromthis stopp e was to provide the installation with one or more sparestokers which could be brought into operation when others failed. Thisis, of course, an extremely expensive and cumbersome arrangement.

The foregoing drawbacks are eliminated in the present invention by theprovision in each installation of at least two electric driving motors,under the control of means such that the supply of fuel to the furnacemay be adjusted either manually by electromagnetically operatedequipment connected in the supply circuits of the motors, orautomatically by electrically operated means responsive to the rise andfall of the temperature of the water and/or the rise and fall of thesteam pressure in the boiler. Through the operation of the automaticmeans the stoker installation operates without any attention so as toprovide the amount of heat required at any given moment. In addition,the automatic arrangement includes means whereby upon the failure of oneof at least two electric driving motors, another one of the motors willbe automatically and instantly brought into effective operation. Whilesuch an arrangement requires the provision of one or more additionaldriving motors, the expenditure for additional complete spare stokers iseliminated, to-

gether with the additional space and equipment which they require. I I

Figure 1 is an elevational view of a stoker driving arrangementemploying two motors; Figures 2 and 3 illustrate detailed views of thefree-wheeling device shown in Figure 1; Figure 4 illustrates anarrangement similar to that illustrated in Figure 1, but employing gearwheel drives instead of belts and pulleys; Figure 5 is a view similar toFigure l, but with three-instead of two motors; Figures 6 and 7illustrate diagrammatically switches and circuits employed with thetwomotor arrangement; and Figure 8 illustrates a switch arranged in theair duct leading from the fan to the stoker.

Referring to the accompanying drawings, Figure 1 is a diagrammatic andelevational view partly in section showing a stoker driving arrangementhaving two electric motors coupled singly and independently of eachother to the stoker in a manner to act as the driving medium for thefuel feeding device and for at least one fan.

The numerals I and 2 designate the electric motors, with the motor Idriving a worm shaft 4 through a pair of pulleys and a wedge belt 3. Theworm shaft 4 drives one or more sets of gear wheels 8 and l by means ofthe worm wheel 5. The shaft 8 of the gear wheel I is connected to thefuel feeding device (not shown).

The electric motor 2 drives the shaft III by means of pulleys and awedge belt 9, and the fan I2, by means of the belt I I and pulleysshown. A known type of free wheeling device I3 is connected between theworm shaft 4 and the shaft III. The free wheeling device consists of anexternal rim it fixed to the worm shaft 4, and a core I5 fixed to theshaft III, with rollers I6 interposed therebetween to effect thetransmission of power from the core to the rim.

When the motor 2 is driving the stoker and the motor I isdeenergized,the shaft I0 drives the worm shaft 4 and thereby the fuelfeeding device (not shown). This takes place because, as the motor 2starts, the rollers I6 are pressed outwardly against the rim It by thecore I5 and the corresponding shafts thereby become operativelyconnected.

If, instead of the motor 2, the motor I is started, the rate ofrevolution of the worm shaft 4 is higher because the gear ratio betweenmotor I and the worm shaft 4 is greater than that between the motor 2and the worm shaft 4. As the rim I4 thereby attains a higher rate ofrevolution than the core I5, the rollers I6 recede from the rim It. Thisaction of the free-wheeling device disconnects motor 2 and motor I aloneis operatively connected to, and drives the fuel feeding device, whilemotor 2 alone drives the fan. It is evident, therefore, that the amountof fuel supplied to the furnace b dependent upon which of the motors iscoupled to the fuel feeding device (not shown).

Figures 2 and 3 illustrat in detail the construction of thefree-wheeling device II. The numeral I4 designates the outer rim whichis fixed to the worm shaft 4, the core It being fixed on the shaft III,the rollers I6 being interposed between the rim and the core. When thecore I is rotated in the direction of the arrow relative to the rim [4,the rollers [8 are driven along the oblique surfaces in the recesses ofthe core and become pressed against the rim so that the latter is turnedalong with the core, so that the two shafts become operatively connectedand turn in the direction originated by the shaft III. Whenever the rimI4 is rotated in the direction of the arrow at a higher speed than thecore II, the rollers I5 recede along the said oblique surfaces in adirection away from the rim l4, and the shafts 4 and III aredisconnected and can rotate independently of each other. Freewheelingcouplings of the type described are well known in the art, and thatdescribed herein forms, per se, no part of the present invention.

Referring to Figure 4 of the drawings, the arrangement therein shown,involving two motors and 2, corresponds in every essential respect withthe arrangement of Figure l, with the exception that gear wheel drives35, 36 and 3! are used instead of the belts 3, 9 and IS and attendantpulleys.

Figure 5 of the drawings shows an arrangement involving thre electricmotors designated ii, if! and 88, respectively, which are operativelyconnected to corresponding shafts 23, 24 and 25 b means of wedge belts25, 2! and 22, respectively, with free-wheeling devices 26 and 21coupied between each two adjacent shafts.

The shaft :2 drives the worm wheel 29 by means of the worm 28, the wormwheel being connected through gear wheels 30 and 3I to the fuel feedingdevice (not shown) through shaft 32.

The motor I9 drives the combustion air fan 34 through the belt 33 andattendant pulleys. When only motor I 9 is started it drives the fan 34as well as the shaft 25, and through the free-wheeling devices 21 and26, also the shafts 24 and 23, whereby the fuel feeding device is drivenat low speed.

From the foregoing it is evident that by reason of the presence of thefree wheeling devices 26 and 21, any of the three motors can,independently of each other, drive the fuel feeding device,

at correspondingly different speeds depending upon the ratio of theiroperative connections to the corresponding shafts. In addition, thethree motors can each have several speeds, thereby in effect providingthe stoker with several additional selective speeds.

it be desired to use more than three motors, the construction and mannerof operation corresponds to that shown in Figure 5, with the exceptionthat an additional free-wheeling device must be used for each extramotor.

In Figure 6, the numerals I and 2 designate the electromotors of whichmotor I may have two or more speeds. The device 38 can be an ordinarymultiple point switch having several contacts enabling initially closingthe circuit to the motor 5 and then changing over to the two or moredifferent speeds of the motor I. The device I! Is an ordinary switch bymeans of which the current supply to the motors I and 2 can be closed oropened, and the device 4| is a: automatic switch of conventional typereacting either to rising and falling water temperatures or to risingand falling steam pressures in the boiler fired by the stoker.

When the current supply is closed by manual operation of the switch 39,and the automatic switch 40 is closed, then the motor 2 is the first tostart, and it drives the fuel feeding device at lowest gear ratio aswell as the fan. If now the circuit to motor I is closed by means of theswitch 38, then this motor, which drives the fuel feeding device at ahigher speed than motor 2, will take care of the operation of thefeeding apparatus, while motor 2 is automatically uncoupled from shaft 4by means of the free wheeling device I3 (Figure l), but continues todrive the fan. By adjusting the position of the switch 38, the speed ofmotor I may be increased to give to the fuel feeding device a stIllhigher speed, while motor 2 continues to drive the fan. The switches 38and 29 may be located remote from the fuel feeding device, in such amanner that stopping and starting as well as the gear changing of thefuel feeding device can be done by remote control.

Figure 7 shows an arrangement involving two motors I and 2, the firsthaving two or more speeds. The numerals 41, 42 and 43 designateautomatic switches of conventional type which react either to rising andfalling water temperatures or to rising and falling steam pressures inthe boiler fired by the stoker. When the stoker is started by manualclosing of the switch 29, and the switch 4| is closed, the motor 2 willstart, and drive the fuel feeding device at lowest gear ratio as well asthe fan. By means of the switch 42 current is subsequently supplied tomotor I which then by itself drives the feeding device at a higherspeed, since the motor 2 is uncoupled automatically from the feedingdevice by means of the free wheeling device l3, but continues to drivethe fan. By means of the switch 43 motor 1 may be run at one of itshigher speeds, whereby the feeding device will run at a higher speed,while motor 2 continues to drive the fan.

The number of different speeds available for the stoker depends upon thenumber of motors provided in the driving arrangement and upon the numberof speeds possessed by each motor. In the drawings, motor I is assumedto have two speeds and motor 2 one speed.

When the switch 43 is opened automatically, as at too high a watertemperature for the heat requirements or at too high a steam pressure,then the higher speed circuit of motor I will be broken, while the lowspeed circuit of motor I is held closed by the switch 42, so that thestoker is operated at low speed. Upon any further rise of the watertemperature or the steam pressure in the boiler, the switch 42 willbreak the connection to the lowest speed circuit of motor I, and motor Iwill stop, after which motor 2 becomes coupled by means of the freewheeling device II to the fuel feeding device at the lowest gear ratio,whereat the motor 2 acts to drive the fuel feeding device as well as thefan. If then the water temperature or the steam pressure rises stillhigher, the switch 4| will automatically break the circuit to motor 2,whereupon the stoker stops entirely. Upon the falling of the watertemperature or steam pressure responsive to rising consumption of heat,the stoker is started in the lowest gear ratio by automatic switch 4|,and then automatic adjustments of the stoker will be producedsuccessively, from a lower to a higher, and thence to a still highergear ratio, as the switches 42 and 43 are closed successively.

If the stoker has three motors, as shown in Figure 5, the abovedescribed automatic switching arrangement will correspondingly close orbreak the circuits of the motors I1 and I8, which drive only the fuelfeeding device and not the fan. In all other respects the manner ofoperation with three or more motors is similar to that described abovefor two motors. The automatic switches 4|, 42 and 43 per se do not formparts of the present invention.

In the arrangement shown in Figure 1 involving two motors actingindependently of each other through the free wheeling device 13, theoperation of the motors may be controlled by the automatic switches 4|,42 and 43, whereby there is obtained the advantage, not only that thestoker starts and stops automatically, but that the stoker automaticallychanges gear in such a manner that the speed of the fuel feeding device,and hence the rate of fuel supply, closely follows the variations in theheat requirements.

In the described arrangement, should motor I fail for any reason, thesupply of fuel to the furnace will not stop, since in that case motor 2automatically couples to the fuel feeding device through the freewheeling device H at lowest gear ratio, so that operation of the stokercontinues in this gear ratio. Therefore, cessations in operation of thestoker occur less frequently so that the need for spare stokers isgreatly reduced or eliminated.

In the arrangement of Figure 8, of the drawings, a switch is arranged inthe air duct 44 leading from the fan of the stoker, consisting of atilting or swinging device, for example a plate 46 which is fixed on arotatable shaft 45 projecting into the air duct 44 and carrying on itsouter end an electric contact 41 to close or break the circuit of themotor I exclusively driving the fuel feeding device but not the fan. InFigure 8 the switch 41 is shown as a mercury switch. In the position ofrest, the plate is in vertical position and the switch 41 is open. If,with the switch in this position, motor 2 is started, fan [2 will beoperated, and the resultant air pressure in the air duct 44 will tiltthe plate 46, and thereby close the mercury switch 41, so that currentcan reach the motor I.

By means of this arrangement cooperation is established between theoperation of the fan and the operation of the fuel feeding device, sincethe motor I cannot drive the fuel feeding device un- I less the fan isrunning. Should the fan stop, when, for example, the fuses of the motor2 blow out, the switch 41 breaks the circuit to motor I, and motor I isautomatically stopped. Thus, by means of the switch 41 the supply offuel to the furnace is halted whenever the amount of air required forcombustion of the fuel is not supplied by the fan.

Iclaim:

In a driving arrangement for a mechanical stoker having fuel feed meansand a fan, a first driving shaft, means for driving the fuel feed meansfrom said first driving shaft, a first electromotor, permanent couplingmeans between said first electro-motor and said first driving shaft todrive said shaft at a predetermined minimum speed when said motor isrunning, a second driving shaft, a second electro-motor, permanentcoupling means between said second electromotor and second driving shaftto drive the latter at a speed less than said minimum speed of saidfirst driving shaft, a permanent coupling between said secondelectro-motor and said fan to drive the fan at a constant speed, and afree Wheel coupling between said second driving shaft and said firstdriving shaft to drive the latter from the former when said first motoris not running.

JORGEN .HELGE JACOBSEN.

